MBs are non-transferable for admission. They must be used for the person assigned when entering. They say you can transfer FPs. Good luck getting the majority of people trying to figure that out with the app. Easier just to hand over your MB to another member of your party. Again, even if you remaIn in the park and intend to sit out a ride, why let your FP+ take up space in the system? Yes, you could cancel it. But is it really such a sin to hand over your MB to, say, your daughter and let her ride while you wait? If you have a larger party, there tends to be one person who scheduled all the FPs for the whole group anyway. Handing over the MB isn't adding any more than what was scheduled for the group already.
The difference from the old system is that you could only do this with someone you know. In the old system you could give your FP to a complete stranger. Can't do that with an MB. If you did, now THAT would be wrong.